1. Field of the Invention
The present invention relates to a controller which manages a secondary controller for controlling sheet (or paper) carrying in an image formation apparatus or the like.
2. Related Background Art
In an image formation apparatus such as a laser beam printer or the like, page control information and printing information are formed in page units upon analyzing page description language (PDL) inputted from a host computer. Then, a selective control of a recording sheet feed unit and a recording sheet discharge unit is performed based on the page control information, and an image corresponding to the printing information is formed on a sheet.
More particularly, in the laser beam printer recently proposed, there are provided a video controller for forming the page control information and the printing information upon analyzing the page description language from the host computer, an engine controller for controlling an image formation unit in accordance with the page control information and the printing information from the video controller, and an optional controller for controlling optional units which perform a sheet feeding process, a sheet discharging process and a sheet stapling process in accordance with the page control information from the video controller. In order to cope with a case where a sheet carrying distance from the optional unit for feeding a sheet to a printer is long, it has been proposed that the page control information be used for a page on which an image is formed after several pages or several tens of pages are previously transferred to the optional controller from the video controller.
In such a laser beam printer as proposed above, the video controller previously transfers the page control information that is later managed to the optional controller and the engine controller. Then, the video controller manages a timing of the control performed in the optional controller and the engine controller, whereby a maximum throughput can be obtained.
However, in this structure, if it is considered that there is no stapling member (i.e., stapling needle) in the optional unit which performs the sheet stapling process after the video controller transfers the page control information including the stapling process to the optional controller, the optional controller is going to execute the page control information already transferred from the video controller, as it is. Therefore, there occurs such a problem as the process is advanced without being supplied with the stapling member.
Although it is required to perform a cleaning operation on a photosensitive drum after executing a jamming process of recording sheets, like the above problem, since the optional controller is going to execute the page control information already transferred as it is after the sheet jamming process, there occurs such a problem as the process is advanced without performing the cleaning operation.